pub fn silverman_bandwidth(data: &[f64]) -> Result<f64, StatsError>Expand description
Silverman’s rule-of-thumb bandwidth:
h = 0.9 * min(std, IQR/1.34) * n^(-1/5).
Uses the sample standard deviation (n − 1 denominator). Returns
StatsError::InvalidBandwidth when the estimate is not finite and
positive — e.g. fewer than two points, or an all-identical sample where both
the spread and the IQR are zero.